Pulsato generation system

ABSTRACT

Pulsato is generated by the acoustical mixing of sounds emitted from two frequency shift channels. In one channel a musical or other signal is frequency shifted upwardly by several Hertz, and in a second channel the frequencies are shifted downwardly by a like amount. The listener perceives a pleasing pulsato effect at a frequency equal to the sum of the frequency deviation introduced in the two channels. In another embodiment, a third channel reproduces the musical signal unshifted in frequency. The sounds emitted from the frequency shift channels interact with the audio output from the third channel to produce a pulsato having a frequency equal to the frequency shift of either channel. As defined herein, &#39;&#39;&#39;&#39;pulsato&#39;&#39;&#39;&#39; is a term meaning cyclic variation of an otherwise relatively constant component or components of music or musical tones at the rate of from five to eight cycles per second. If the only varied component is frequency characteristic of the tone, then the pulsato is vibrato. If the only varied component is amplitude, then the pulsato is tremolo. Other musical components may be varied to produce pulsato.

iinited States Patent 1 91 Leslie 1 Oct. 15, 1974 PULSATO GENERATION SYSTEM [76] Inventor: Donald J. Leslie, 1561 Gaywood Dr., Altadena, Calif. 91001 22 Filed: Aug. 16, 1972 21 Appl. No.: 280,997

Primary Examinerl(athleen H. Claffy Assistant Examiner-Douglas W. Olms Attorney, Agent, or Firm-Flam & Flam [57] ABSTRACT Pulsato is generated by the acoustical mixing of sounds emitted from two frequency shift channels. In one channel a musical or other signal is frequency shifted upwardly by several Hertz, and in a second channel the frequencies are shifted downwardly by a like amount. The listener perceives a pleasing pulsato effect at a frequency equal to the sum of the frequency deviation introduced in the two channels. In another embodiment, a third channel reproduces the musical signal unshifted in frequency. The sounds emitted from the frequency shift channels interact with the audio output from the third channel to produce a pulsato having a frequency equal to the frequency shift of either channel.

As defined herein, pulsato is a term meaning cyclic variation of an otherwise relatively constant component or components of music or musical tones at the rate of from five to eight cycles per second. if the only varied component is frequency characteristic of the tone, then the pulsato is vibrato. If the only varied component is amplitude, then the pulsato is tremolo. Other musical components may be varied to produce pulsato.

9 Claims, 4 Drawing Figures FREQUENCY CHANGING DEVlCE (-i) 25\ FREQUENCY /5O CHANGING W DEVICE F) ems. a2 E e w 29 time... 38

-F LATv PAIENTEDUU I 51914 Smear:

Ira 4,

33 AMP! FREQUENCY /30 CHANGING DEVICE (+f) -5HARP- DRIVE MEANS 22" FREQUENCY CHANGING VICE("f) -FLAT PULSATO GENERATION SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of pulsato by the acoustical mixing of sounds emitted from two channels wherein a musical signal respectively is shifted upwardly and downwardly in frequency.

2. Description of the Prior Art The addition of pulsato, tremolo, chorus or other low frequency modulation effects to a musical signal enhances the richness of the resultant sounds. Pulsato may be produced using rotary sound channels, as shown in the inventor's U.S. Pat. Nos. Re 23,323, 3,080,786 and 3,174,579 among others. Tremolo also may be introduced electronically, using stationary speakers, as shown for example in the inventors U.S. Pat. No. 2,899,644. The present invention has as an objective the generation of pulsato without the use of a rotating speaker, and free of certain shortcomings associated with pulsato produced completely electronically in a single audio channel.

One prior art problem concerns the production of tremolo for a complex wave signal like that from an electronic organ. Such signals are exceedingly difficult to tremolo without having the fourth and fifth interval harmonic beats substantially destroy the result. One way to solve this problem is to provide separate amplifiers and acoustical channels for alternate notes in the octave, as shown in the inventors U.S. Pat. No. 2,596,258 and 3,049,040. Pulsato may be introduced in such a system without detrimental interval beat effects. However. separate timbre, swell control and other circuits must be provided thus increasing cost of the instrument and making it impractical to use such an approach on existing instruments. Thus another objective is to provide a system capable of generating pulsato for a complex wave signal without producing fourth and fifth interval harmonic beats and without the need for electronically isolating every other note in the oc- SUMMARY OF THE INVENTION These and other objects of the invention are achieved by generating pulsato through the acoustical mixing of sounds emitted from two frequency shift channels. In the first channel a musical or other signal continuously is shifted upwardly in frequency by several Hertz, and in the other channel the same signal is frequency shifted downwardly by a similar amount. The resultant signals are reproduced by stationary, physically separated speakers. The emitted sounds interact to produce a pulsato effect at a frequency equal to the sum of the frequency shifts introduced in the two channels.

In a preferred embodiment the musical signal, unshifted in frequency. also is reproduced by a third audio channel including a third speaker. The sounds emitted from the frequency shift channels each interact with the unshifted audio output to provide pulsato at a frequency equal to the deviation introduced in either frequency shift channel. The listener perceives a particularly pleasing pulsato effect. The sound appears to float around the room, rather than emanate from a fixed location.

The pulsato produced by the present invention appears predominantly to be an amplitude effect. The system is useful with electric pianos as well as organs. The invention finds particular applicability with that type of musical instrument wherein the sounds from a struck bar are amplified electronically; when so employed, a vibraharp type sound is achieved. It is to be noted that since there are two sources of shifted frequencies at all times, the average pitch heard will remain true at all times even on short duration staccato passages. This advantage does not obtain with the usual vibrato as the signals may be sharp, flat or average at different points in time.

BRIEF DESCRIPTION OF THE DRAWINGS A detailed description of the invention will be made with reference to the accompanying drawings in which:

FIG. 1 is an electrical block diagram of a two channel pulsato generation system in accordance with the present invention.

FIG. 2 is an electrical block diagram of a pulsato generation system employing two frequency shift channels and a third channel in which the input signal is not shifted in frequency.

FIG. 3 is an electrical diagram of a frequency changing device useful in the system of FIG. 1 or 2.

FIG. 4 is an electrical block diagram of a pulsato generation system similar to that shown in FIG. 2, but with the addition of a fourth rotary pulsato channel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description is of the best presently contemplated modes of carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention since the scope of the invention best is defined by the appended claims.

Structural and operational characteristics attributed to forms of the invention first described also shall be attributed to forms later described, unless such characteristics obviously are inapplicable or unless specific exception is made.

A first embodiment of the inventive apparatus for providing pulsato is shown in FIG. 1. A musical signal supplied via a terminal 11 is fed to a pair of audio channels 12, 13. In the first channel 12, the musical signal is shifted upward (sharp) in frequency by a frequency changing device 14. The frequency shift +f preferably is between 0 and about 16 Hz. The output of the device 14 is supplied via a balance control 15 and an amplifier 16 to a speaker 17. In the other audio channel 13, a frequency changing device 18 shifts the musical signal downward (flat) in frequency by a like amount f. The output of the device 18 is supplied via a balance control 19 and an amplifier 20 to a speaker 21 which is physically separated from the speaker 17. The frequency changing devices 14, 18 may be of the type shown in FIG. 3 and preferably are interconnected by a common drive means 22 so that the frequency shift in each frequency shift channel will be substantially equal.

The sounds emanating from the speakers 17, 21 will interact to produce an acoustic pulsato or tremolo having a frequency equal to the sum of the frequency deviation introduced by the devices .14 and 18. Thus if the channel 12 signal is shifted upwardly by 3 Hz and the channel 13 signal is shifted downwardly by 3 Hz, the pulsato effect will have a frequency of 6 Hz.

Note that the output from each of the speakers 17, 21 contains no pulsato effect whatever. The pulsato results from the acoustical mixing or interference between the sound outputs. This produces a very pleasing tremolo completely free of the harsh sounds usually experienced with tremolo or vibrato produced electronically in a single channel. The changing phase relation ships of the speaker outputs produce a sound which appears to float around the room rather than originate at a certain point.

In the embodiment of FIG. 2, three audio channels 26, 27, 28 are employed. In the channels 26, 27 the musical signal supplied via a terminal 29 is shifted respectively upward and downward in frequency by the same amount, using frequency changing devices 30, 31 which may be of the type shown in FIG. 3. The frequency changing devices 30, 31 may be interconnected by common drive means 22' so that the frequency shift in each frequency shift channel will be substantially equal. The upwardly shifted signal from the device is supplied via a balance control 32 and an amplifier 33 to a speaker 34; the downwardly shifted signal is supplied via a balance control 35 and an amplifier 36 to a speaker 37. In the third channel 28, the original musical signal, unshifted in frequency, is supplied via a balance control 38 and an amplifier 39 to a speaker 40. The speakers 34, 37 and 40 preferably are physically separated from each other.

The sound outputs of each speaker 34, 37 beat against the unshifted audio signal reproduced by the speaker 40 to produce a very pleasing pulsato effect at a frequency equal to the deviation introduced by either frequency changing device 30 or 31. For example, if

the device 30 shifts the musical signal upward in frequency by '7 Hz, and the device 31 shifts the signal downward by 7 Hz, the resultant pulsato will have an effective frequency of 7 Hz. The pulsato produced by the three channel system of FIG. 2 typically will have an even more pronounced floating effect than that obtained with the system of FIG. 1.

To obtain the same effective pulsato frequency, the two channel system of FIG. 1 requires that the devices 14, 18 introduce a frequency deviation one-half that introduced by each frequency changing device 30, 31 of the three channel system of FIG. 2. For this reason. the pulsato effect produced by the twochannel system will not be as deep" as that produced by the system of FIG. 2.

Different pulsato effects can be achieved by appropriate selection of the amount of frequency shift introduced by the frequency changing devices. For example, if the frequency deviation is selected to provide a pulsato frequency in the range of about 4 Hz to 7 Hz, a tremolo effect is achieved. With a lesser frequency deviation. a chorus effect results. Pulsato frequencies above the tremolo range produce other effects particularly useful to enhance percussion sounds. Each frequency changing device 14, 18, 30, 31 may be preset to provide a fixed frequency deviation, or may be adjustable to allow control by the musician of the effective pulsato frequency. Alternatively, the amount of shift may be varied continuously.

Other variations of the invention may be employed to produce different acoustic effects. For example, the frequency deviation in the upwardly shifted channel may differ slightly from that in the downwardly shifted channel. Parallel systems at different pulsato speeds may be employed.

The invention also may be used in conjunction with a rotating speaker pulsato generator, as shown in FIG. 4. The system of FIG. 4 incorporates all three channels of the system shown in FIG. 2. In addition, the musical signal from the terminal 29 also is supplied to another audio channel 41 including a balance control 42, an amplifier 43 and a rotating speaker enclosure 44 having a pair of oppositely facing speakers 45, 46. The enclosure 44 typically, but not necessarily, is rotated at onehalf the pulsato frequency. For example, with frequency changing devices 30, 31 respectively set to introduce a frequency deviation of +6 Hz and 6 Hz, thereby producing a 6 Hz pulsato, the enclosure 44 may be rotated at about three revolutions per second.

The outputs of the four audio channels are balanced using the controls 32, 35, 38, 41 to produce a very pleasing complex wave pulsato with a minimum of interval harmonic beating. This reduced harmonic beating results from the reduced frequency shift in the usually difficult harmonic frequency range of 700 Hz to 1,800 Hz'as compared with conventional electronic vibrato or tremolo systems, and also results from the complex audio mixing ofthe sounds from four different audio channels.

An exemplary frequency changing device 50 useful with the present invention is shown in FIG. 3. This device 50 is of the type disclosed in the inventors U.S. Pat. Nos. 3,251,924 and 3,372,225. The incoming musical signal supplied on a line 51 is fed to a broadband phase splitter 52 providing four outputs differing in phase by 0, and 270 with respect to each other. These signals are fed respectively to four equiangularly arrayed stationary plates 53, 54, 55, 56 of a rotary capacitor 57. The capacitor 57 also includes a rotor plate 58 eccentrically mounted with respect to the center of the stationary plates 53 56. A motor 59 having an optional speed control 60 rotates the plate 58 at a selected speed.

The output from the capacitor 57, present on a line 61 will differ in frequency from the input on the line 51 by a frequency shift equal to the rate of rotation of the plate 58. Thus if the motor 59 is set to rotate the plate 58 at six revolutions per second, the input signal will be shifted by 6 Hz. The direction of rotation of the plate 58 will determine whether the frequency is shifted upwardly or downwardly.

Circuitry for the phase splitter 52 is conventional. One form of circuitry is shown in the above-mentioned U.S. Pat. No. 3,251,924 to D. J. Leslie. Another applicable circuit is shown in the copending U.S. application Ser. No. 183,845. In conjunction with an ac motor 59, the speed control 60 may comprise an ac power supply of adjustable frequency. The motor 59 4 speed, and hence the frequency shiftintroduced by the device 50, then can be controlled by adjusting the ac supply frequency.

In the optional embodiment of HO. 2, the speakers 45, 46 may be driven either in phase or out of phase. When driven out of phase, some unusual effects result, with pulsato being produced both at the shift frequency established by either device or 31 and at one-half this shift frequency.

Intending to claim all novel, useful and unobvious features shown or described, the applicant claims:

1. In a pulsato generation system for use with an electrical musical instrument:

a. circuit means forming an electrical output channel deriving electrical signals from said instrument corresponding to all notes in a musical range;

b. a pair of separate frequency shift channel means each connected to said circuit means so that the same musical information is applied to each frequency shift channel means;

c. one of said frequency shift channel means including means shifting said signals upwardly in frequency and further including a speaker for translating said signals into sound;

d. the other of said frequency shift channel means including means shifting said signals downwardly in frequency and further including a speaker for translating said signals into sound;

e. the acoustic interaction of the sounds produced by said speakers producing pulsato by virtue of the frequency shift of the signals;

f the frequency shift in each of said frequency shift channels being substantially equal whereby a single, true pitch, pulsato sound is perceived by the listener.

2. A system according to claim 1 further comprising:

third channel means including a third speaker for translating said input signals into sound without shift in frequency, the sounds emitted by said first, second and third speakers acoustically interacting to produce pulsato.

' 3. A system according to claim 1 wherein each frequency shift channel means includes a frequency changing device for shifting the frequency of said input signal by an amount in the range of from 0 to about 16 Hz.

4. A system according to claim 1 together with means for controlling the amount of frequency shift introduced by said devices.

5. A system according to claim 3 wherein each of said frequency changing devices comprises:

a phase splitter for deriving from the input signal,

components having progressively shifted phase angles, and

rotational capacitor means including a plurality of equiangularly spaced stator plates receiving said progressively phase shifted components and an eccentric, rotary pick-up plate driven at a selectable rate and supplying as an output a signal shifted in frequency by an extent corresponding to said rate.

6. A system according to claim 2 wherein said first,

second and third speakers all are stationary and are separated from each other.

7. A system according to claim 6 further comprising a fourth audio channel including a mechanically rotating speaker assembly for reproducing said input signal.

8. A system according to claim 7 wherein said rotating speaker assembly comprises a pair of diametrically oppositely facing speakers mounted in a common rotatable enclosure rotated at a rate approximately equal to one-half the frequency shift introduced by either of said frequency changing devices.

9. In a pulsato generation system for use with an electrical musical instrument:

a. circuit means forming an electrical output channel deriving electrical signals from said instrument corresponding to all notes in a musical range;

b. a pair of separate frequency shift channel means each connected to said circuit means so that the same musical information is applied to each frequency shift channel means;

c. one of said frequency shift channel means including means shifting said signals upwardly in frequency and further including a speaker for translating said signals into sound;

d. the other of said frequency shift channel means including means shifting said signals downwardly in frequency and further including a speaker for translating said signals into sound;

e. the frequency shift in each of said frequency shift channels being substantially equal whereby the pitch of the pulsato sound remains true;

f. a third channel means including a third speaker for translating said input signals into sound without shift in frequency;

g. the sound produced by said first, second and third speakers acoustically interacting to produce pulsato;

h. said frequency shift channels each including a controllable device for shifting frequency in an range of from 0 to 16 Hz, each device comprising a phase splitter for deriving from the input signals,

components having progressively shifted angles; and

rotational capacitor means including a plurality of equiangularly spaced stator plates receiving said progressively phase shifted components and an eccentric, rotary pick-up plate driven at a selectable rate and supplying as an output, a signal shifted in frequency by an extent corresponding said rate;

. and a fourth channel means connected to said circuit means including a mechanically rotating speaker assembly for translating said signals into sound, said speaker assembly including a pair of diametrically oppositely facing speakers mounted in a common rotatable enclosure rotated at a rate approximately one-half the frequency shift introduced by said frequency changing devices. 

1. In a pulsato generation system for use with an electrical musical instrument: a. circuit means forming an electrical output channel deriving electrical signals from said instrument corresponding to all notes in a musical range; b. a pair of separate frequency shift channel means each connected to said circuit means so that the same musical information is applied to each frequency shift channel means; c. one of said frequency shift channel means including means shifting said signals upwardly in frequency and further including a speaker for translating said signals into sound; d. the other of said frequency shift channel means including means shifting said signals downwardly in frequency and further including a speaker for translating said signals into sound; e. the acoustic interaction of the sounds produced by said speakers producing pulsato by virtue of the frequency shift of the signals; f. the frequency shift in each of said frequency shift channels being substantially equal whereby a single, true pitch, pulsato sound is perceived by the listener.
 2. A system according to claim 1 further comprising: third channel means including a third speaker for translating said input signals into sound without shift in frequency, the sounds emitted by said first, second and third speakers acoustically interacting to produce pulsato.
 3. A system according to claim 1 wherein each frequency shift channel means includes a frequency changing device for shifting the frequency of said input signal by an amount in the range of from 0 to about 16 Hz.
 4. A system according to claim 1 together with means for controlling the amount of frequency shift introduced by said devices.
 5. A system according to claim 3 wherein each of said frequency changing devices comprises: a phase splitter for deriving from the input signal, components having progressively shifted phase angles, and rotational capacitor means including a plurality of equiangularly spaced stator plates receiving said progressively phase shifted components and an eccentric, rotary pick-up plate driven at a selectable rate and supplying as an output a signal shifted in frequency by an extent corresponding to said rate.
 6. A system according to claim 2 wherein said first, second and third speakers all are stationary and are separated from each other.
 7. A system according to claim 6 further comprising a fourth audio channel including a mechanically rotating speaker assembly for reproducing said input signal.
 8. A system according to claim 7 wherein said rotating speaker assembly comprises a pair of diametrically oppositely facing speakers mounted in a common rotatable enclosure rotated at a rate approximately equal to one-half the frequency shift introduced by either of said frequency changing devices.
 9. In a pulsato generation system for use with an electrical musical instrument: a. circuit means forming an electrical output channel deriving electrical signals from said instrument corresponding to all notes in a musical range; b. a pair of separate frequency shift channel means each connected to said circuit means so that the same musical information is applied to each frequency shift channel means; c. one of said frequency shift channel means including means shifting said signals upwardly in frequency and further including a speaker for translating said signals into sound; d. the other of said frequency shift channel means including means shifting said signals downwardly in frequency and further including a speaker for translating said signals into sound; e. the frequency shift in each of said frequency shift channels being substantially equal whereby the pitch of the pulsato sound remains true; f. a third channel means including a third speaker for translating said input signals into sound without shift in frequency; g. the sound produced by said first, second and third speakers acoustically interacting to produce pulsato; h. said frequency shift channels each including a controllable device for shifting frequency in an range of from 0 to 16 Hz, each device comprising a phase splitter for deriving from the input signals, components having progressively shifted angles; and rotational capacitor means including a plurality of equiangularly spaced stator plates receiving said progressively phase shifted components And an eccentric, rotary pick-up plate driven at a selectable rate and supplying as an output, a signal shifted in frequency by an extent corresponding said rate; i. and a fourth channel means connected to said circuit means including a mechanically rotating speaker assembly for translating said signals into sound, said speaker assembly including a pair of diametrically oppositely facing speakers mounted in a common rotatable enclosure rotated at a rate approximately one-half the frequency shift introduced by said frequency changing devices. 